Indian officials say heavy rain and darkness have temporarily halted rescue operations after at least 103 people drowned when an overcrowded ferry capsized on one of India's largest rivers.

Efforts to find more than 100 people still missing are set to resume Tuesday morning.

Jayanta Choudhury, the police chief of Assam state, where the boat sank in the fast-flowing Brahmaputra River, said about 100 people either were rescued or managed to swim to safety in the Dhubri district, near the border with Bangladesh.

The double-decker ferry carrying about 300 passengers broke into two pieces after capsizing late Monday in the swollen river. The boat was overloaded with people, sacks of rice and other goods, and carried no lifeboats or life jackets.

The accident is the worst of its kind in recent memory in India's northeastern region. Rescuers were hampered by torrential pre-monsoon rains and heavy winds.

Indian authorities say they contacted officials in Bangladesh for help in the search for survivors. Prime Minister Manmohan Singh said he was "shocked and grieved" by the incident.

The Brahmaputra, one of Asia's largest rivers, originates in Tibet, and flows through India and Bangladesh and into the Bay of Bengal.